| I am re-visiting this -- time to add custom pseudo-elements to Shadow
| DOM spec! -- and would like to solicit ideas/opinions on the topic of
| collisions.
I'm in favor of a user prefix. Since 'x-' happens to be the preferred one,
why not 'x-'.
However, I'm unsure about your goal here. Do you intend [[ #id::x-element ]]
to match more than one element? Because if you want this, custom
pseudo-elements aren't the right tool for you. In that case, you need a
custom pseudo-class and a "shadow-walking" operator. Something like:
#id .. div:x-selected { ... }
Custom pseudo-classes were already proposed in the past (but died because of
weak traction) so this isn't a non-sense to reintroduce them now we have
good use cases for them.